ELE 211 HW CH1

_________ current applied to a conductor starts at zero and goes to its maximum value almost instantly when a switch is closed.

direct

The _______ rule is an explanation of the direction of a magnetic field around a coil relative to the direction of the current in the coil, where a left hand is used to illustrate the relationship.

left-hand coil

A(n) __________ is a force produced by a magnet that exerts a force on moving electric charges or on other magnets.

magnetic field

The basic law of ________ states that unlike magnetic poles (N and S) attract each other and like magnetic poles (N and N or S and S) repel each other.

magnetism

A __________ material is a material that can be weakly magnetized in the same direction as the applied magnetic field.

paramagnetic

A _________ magnet is a magnet that can hold its magnetism for a long period of time.

permanent

_______ is a measure of the ability of a material to conduct magnetic flux.

permeability

The ________ of a bar magnet can be determined by suspending it from a point overhead and allowing it to turn freely.

polarity

In order to create the continuous motion needed in a motor, the direction of the current must be _________.

reversed

_________ is the condition where a magnetic core has substantially all the magnetic domains aligned with the field and any increases in current no longer result in a stronger electromagnet.

saturation

The three requirements for induction are a conductor, a magnetic field, and relative motion between the conductor and the magnetic field.

True

Three common naturally occurring magnetic metals are iron, nickel, and cobalt

True

The magnetic field around a straight conductor is relatively weak and must be concentrated for use in an electric motor.

True

The strength of a magnetic field is directly proportional to the number of turns in the coil and the amount of current flowing through the conductor.

True

________ is the temporary magnetic field produced when electricity passes through a conductor.

Electromagnetism

_______ current flow is a description of current flow as the flow of electrons from the negative terminal to the positive terminal of a power source.

Electron

A common ferromagnetic material is copper.

False

A more concentrated, or denser, magnetic flux makes a weaker magnetic force.

False

Common temporary magnets are horseshoe magnets, compasses, and bar magnets.

False

When using the left-hand generator rule, it is assumed that the magnetic field is moving and the conductor is initially stationary.

False

____ is the property of a device or circuit that causes it to store energy in an electromagnetic field.

Inductance

_______ law states that the polarity of the induced voltage is such that it produces a current whose magnetic field opposes the change that produced it.

Lenz's

________ is a force by which materials exert an attraction or repulsion on other materials.

Magnetism

_____ is the ability of an inductor (coil) in one circuit to induce a voltage in another circuit or conductor.

Mutual induction

_________ is a measure of the ability of a magnet to retain magnetism after the magnetizing force has been removed.

Retentivity

________ is the ability of an inductor in a circuit to generate inductive reactance, which opposes change in the current.

Self Induction

A material is nonmagnetic if it has disorganized molecular domains so that the individual fields cancel each other.

True

All magnets have a North (N) and South (S) pole?

True

Any permanent magnet can be demagnetized by a sharp blow or by heat that causes the molecular arrangement to become disorganized.

True

Magnetism is used to produce most of the electricity consumed, develop rotary motion in motors, and develop linear motion in solenoids.

True

The current and strength of the magnetic field decrease if the resistance of the circuit increases.

True

The direction of an electromagnetic field is determined by the direction of the current flowing through the conductor.

True